HIGH INCIDENCE OF OCCULT SPINAL INJURIES FOLLOWING VERTICAL AIRCRACT EJECTION: A PROSPECTIVE STUDY USING MAGNETIC RESONANCE IMAGING

Abstract

Introduction: The use of an ejection seat to escape from a stricken aircraft is associated with the exposure of significant forces. These vertical accelerative forces on the body are in the order of 15–25G with rates of onset of up to 250G per second. Therefore, it is common to see vertical compression fractures, mainly in the thoracolumbar region. Although most vertebral fractures are evident on plain radiographs, subtle spinal injuries elsewhere may not be immediately apparent.

Aim: A prospective study to evaluate for the presence of occult spinal injuries using MRI following aircraft ejection.

Methods: Between 1996 and 2003, 22 ejectees from 18 aircrafts, mean age 32 years (range 24 to 48), were admitted to a regional spinal unit for comprehensive evaluation of their injuries that included whole spine radiographs and Magnetic Resonance Imaging (T1, T2 weighted and STIR sagittal sequences). All ejections occurred within the ejection envelope and were flying below 2000 ft (mean 460 feet) and below 500 knots airspeed (mean 275 knots).

Results: All 5 ejectees (23%) with vertebral compression fractures, one at T6 and 4 in thoracolumbar region, had pain and tenderness in the appropriate area of the spine that was evidently detected on plain radiographs. 3 of these patients with a thoracolumbar fracture (AO A3.3) had more than 50% canal compromise and more than 30 degrees angular kyphosis underwent surgery. Neurological compromise consisting of acute cauda equina syndrome occurred in one patient with a L2 AO A3.3 fracture. More importantly 10 ejectees (45%) had MRI evidence totalling 21 occult thoracic and lumbar vertebral fractures. 4 ejectees had a single occult fracture, 4 had double, 1 had 3 and 1 had 6 occult fractures.

Conclusion: This study confirms the high incidence of occult vertebral injuries following vertical acceleration insult to the spine consequent to emergency aircraft ejection. Once life-saving priority measures have taken place MRI of the entire spine remains mandatory as part the comprehensive evaluation of the patient. Early use of MRI scanning in the management will significantly increase an ejectee’s safe return to flying duties.